Process of and apparatus for producing radiofrequency-current



L. F. FULLER.

PROCESS OF AND APPARATUS FOR PRODUCING RADIOFREQUENCY CURRENT.

' APPLICATION FILED JAN. 19, 1918.

1,381,626. PatentedJune 14, 1921.

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L. f? PUL LEE A TTORNEY6 L. F. FULLER. PROCESS OF AND APPARATUS FOR PRODUCING RADIOFREQUENCY CURRENT.

APPLICATION HLED JAN-19,1918.

Patented June 14, 1921'.

2 SHEETSSHEET Z- WWW/V WWW/M INVENTOR. L,F. FULLER Q WITNESS ATTORNEYS .UNITED STATES PATENT OFFICE.

LEONARD F. FULLER, or sAN FRANCISCO, CALIFORNIA, ASSIGNOR To FEDERAL TELE- GRAPH COMPANY, or sAN FRANCISCO, CALIFORNIA, A CORPORATION or CALI- FORNIA.

PROCESS AND APPARATUS FOR PRODUCING RADIOFREQUENCY-CURRENT.

Specification of Letters Patent. Patented J 14 1921 Application filed January 19, 1918. Serial No. 212,609.

. for Producing Radiofrequency-Current, of

which the following is aspecification.

The invention relates to a process of and an apparatus for producing radio frequency current or oscillations.

An object of the invention is to provide a process of producing radio oscillations or radio frequency current, ,which obviates the use of a spark or an arc.

Another object of the invention is to pro vide a process of producing radio oscillations or radio frequency currents which obviates the use of apparatus having moving or wearing parts.

Another object of the invention is to pro vide an apparatus for producing radio oscillations or radio frequency current which is simple and cheap in construction and which possesses increased reliability and efficiency.

The -invention possesses other advantageous features, some of which. with the foregoing, will be set forth in the following description where I shall outline in full one form of the process of my invention and that specific form of the apparatus which I have selected for illustration in the drawings accompanying and forming part of the present specification. In said specification and drawings I have described one specific form of the process and have shown one specific form of apparatus, but it is to be understood that I .do not limit myself to such forms. since the invention as expressed in the claims may be embodied in a plurality of forms.

Referring to said drawings:

Figure 1 is a diagrammatic representation of the system of my invention for producing radio oscillations.

Fig. 2 is a similar representation of the system for producing radio frequency currents.

Fig. 3 is a diagrammatic representation of the impulse transformer.

Fig. 4 is a graphic representation of the primary transformer current. transformer flux and'secondary transformer voltage.

F ig. 5 is a graphic representation of the produced damped radio frequency oscillations.

Fig. 6 is a graphic representation of the produced undamped radio frequency current.

The method now principally used for the production of radio oscillations is the spark method and the method used for the production of radio frequency currents is the arc method, both of which possess certain inherent disadvantages which it is the object of the present invention to overcome. The apparatus of my invention comprises no moving or wearing parts and may be cheaply and quickly constructed.

My invention may be used for the production of radio frequency oscillations by impulse excitation, in which the radiating circuit is given an electrical impulse and allowed to oscillate before the succeeding impulse occurs, producing a damped wave as shown in Fig. 5. This ivave is similar to that produced by the quenched gap spark system. The invention may also be used to produce a continuous undamped radio fre-- quency current, as is produced by the are system. by imparting to the radiating circuit, impulses which occur at radio frequency, as is shown in Fig. 6.

In the radio frequency ocillationsmethod. I pass a single phase alternating current, preferably of a frequency of 500 or 1000 cycles. through a transformer which is constructed to produce in the secondary, sharp voltage peaks at relatively long time intervals. This type of transformer. which is designated as an impulse transformer. is provided with an isthmus of relative small dimensions with respect to the remainder of the transformer core. so that the isthmus reaches flux saturation before the primary current reaches a maximum and prefe 'ably while the value of the primary current is quite small. Consequently. the flux through the isthmus is constant over the greater portion of the current wave and varies from saturation in one direction to saturation in the other direction during a short interval of the current wave. This rapid variation in flux induces a voltage in the secondary winding which has the same duration as. the flux variation. that is. a fraction of a current wave or cycle. and on account of the rapid change of flux, the

value of the voltage impulse is high. In Fig. 4 I have shown graphically the relation of current, flux and voltage in the transformer, and this showing is merely explanatory, no attempt having been made to show the values relatively. A cycle of current in the primary of the transformer is indicated by the curve 2. The transformer is so constructed that the isthmus reaches saturation when the current value reaches point on the current curve indicated by 3 and remains saturated until the current decreases to the value indicated at point 4. The flux then rapidly decreases to zero and then to saturation in the opposite direction at point 5 on the curve 2. The change in flux from saturation in one direction to saturation in the opposite direction occurs in the brief interval on the cycle between points 4 and 5. The flux is represented by the curve 6. Since the E. M. F. in the secondary is produced by variation of flux in the isthmus, and since it is proportional to the rate of change of the flux, a high voltage'impulse is produced in the secondary, the duration of the impulse being equal to the interval of time between points 4 and 5. The voltage impulses are represented by the curves 7. These impulses are of short duration with relation to the duration of the cycle and occur at time intervals, the intervals being long the duration of the impulses. ties, the relation of the duration of the impulse to the duration of the cycle may be chosen as desired and for the purpose of description I will choose an impulse having a duration of 1/49 the duration of half a cycle, so that time for fortyeight similar impulses is provided between the time of two successive impulses from one transformer. The secondary of the impulse transformer is associated with the radiating circuit, so that the impulses are impressed on the radiating circuit, causing it to oscillate. The impulses follow each other at the frequency of the supply current, for instance 500 or 1000 cycles per sec 0nd, and the circuit oscillates between the impulses, the oscillations gradually decreasing in amplitude until the next impulse. This produces the damped oscillation shown in Fig. 5. The apparatus for producing radio frequency oscillations is shown diagrammatically in Fig. 1. The primary 14 of the transformer 15 is connected to the single phase generator 8 and the secondary 18 of the transformer is connected in series in an oscillating circuit 19 containing the inductance 21 and the capacity 22. The inductance 21 is associated with the inductance 23 in the radiating circuit 24..

To produce an undamped radio frequency current, I provide a method whereby the radiating circuit is excited by successive im- In pracin comparison with pulses occurring at radio frequency as shown in Fig. (3 or at a large fraction of the radio frequency. To produce this result, I produce a multiphase current, preferably by multiplying the phases of a polyphase current and separately transform each phase and impress the impulses produced thereby on the radiating circuit. The transformers produce sharp voltage peaks at relatively long time intervals and these peaks from all of the transformers are combined to produce a more or less continuous wave in the radiating circuit. The electromotive force impulses 7 produced by the plurality of transformers are phased so that they follow each other in proper time sequence to produce the continuous radio frequency current.

Assuming, as before, that the time of duration of an impulse is 1/49 the duration of half a cycle, time is provided between the two successive impulses from one transformer, for forty-eight phased impulses. By providing forty-nine transformers and so timing theimpulses that they are phased and so that a negative impulse from one transformer follows immediately after and forms a continuation of the positive impulse of the preceding transformer, and by combining these impulses. a continuous radio frequency current is produced. Each transformer will produce a positive impulse and a negative impulse for each cycle, so that forty-nine transformers will produce ninety-eight impulses per cycle. With a primary current of one thousand cycles, the frequency of the produced current will be 49,000 cycles per second, which is radio frequency.

The impulses are caused to follow each other in phase by any suitable means, preferably a phase multiplying transformer. Polyphase current, preferably three phase, is fed into the phase multiplying transformer and taps on the phase multnilying transformer winding are connected to the respective impulse transformers. the taps for each impulse transformer being located at diametrically opposite points.

In the construction shown in Fig. 2 of the drawings, the three phase generator 12 is connected to the winding of the phase multiplying transformer 13 at three equidistant points. ,The primary 14: of each impulse transformer 15 is connected to two diametrically opposite points 16-17 of the phase multiplying transformer. The pairs of points of connection of the successive impulse transformer primaries are spaced around the phase multiplying transformer in equal spacing. so that the current cycles follow successively in the successive impulse transformers. The secondary 18 of each impulse transformer is included in an oscillating circuit 19 containing the inductance 21 and capacity 22. The inductances 21 are inductively associated with the inductance 23 in the radiating circuit 24. Signaling may be accomplished in any desired manner, such as by-varying the inductance of. the radiating circuit by the key 25.

It is not essential that sufficient impulse transformers be employed to produce av phased impulse in the radiating circuit at every half cycle of the radio frequency. he number may be reduced-to produce an impulse at each cycle or every other cycle or every third cycle, and so on. The impulse transformer has an isthmus 26 of small cross section with relation to the cross section of the remainder of the core 27, which is so designed that it does not approach saturation. For this reason the isthmus only need be made of the very thin laminations, and the remainder of the core made of cheaper material.

The impulse in construction, so that they may be cheaply made in large numbers. Since a large numher are used at each station, the failure of one or more of them will not interfere materially with the production of a radio frequency current, and will cause only a very slight damping effect in the interval from which the impulse is lacking.

In order to obtain the maximum energy from the impulse transformer, the radiating circuit should be so adjusted that the slope of the radio frequency sine wave should correspond to the analogous slope of the impulse wave produced by the impulse transformer, that is, the sine wave should correspond to the rate of change of the voltage of the impulse wave with respect to time.

I claim:

1. The process of producing radio frequency current from an alternating current, which consists in multiplying the phases of the alternating current, causing each multiplied phase to produce a current having high potential impulses of short duration separated by relatively long time intervals and coordinating the high potential impulses of the multiplied phases to produce a radio frequency current.

2 The process of producing radio frequency current from an alternating current which consists in transforming the alternating current into a plurality of separate alternating currents, transforming each separate transformed current into a current having high potential impulses of short duration separated by relatively long time intervals and impressing the high potential impulses on an output circuit.

3. The process of producing radio frequency current which consists in converting a polyphase alternating current into an alternating current having a greater number of phases, separately transforming each phase of the converted current to produce high potential impulses Of hort duration transformers are identical separated by relatively long time intervals and causing the impulses to act successively to produce radio frequency current.

l. An apparatus for producing radio oscillations, comprising a transformer adapted to convert sinusoidal alternating current into an alternating current having high potentialimpulses of short duration separated by relatively long time periods and an output circuit associated with the secondary of said transformer.

5. An apparatus for producing radio oscillations, comprising a transformer having a magnetic circuit, a portion of which is adapted. to reach flux saturation before the primary current reaches its maximum value, an oscillation circuit including the secondary of said transformer, and an output circuitassociated with said oscillation circuit.

6. An apparatus for producing radio frequency current, comprising a source of alternating current, a phase multiplying transformer connected to said source, a plurality of impulse transformers, each arranged to transform a different multiplied phase and an output circuit associated with the secondaries of the impulse transformers.

7. An apparatus for producing radio frequency current, comprising a source of multi-phase alternating current in which each phase has short high potential impulses separated by relatively long time intervals, means for separately transforming each phase, and an output circuit associated with said transforming means.

8. An apparatus for producing radio frequency current, comprising a source of polyquency current comprising a source of multi-phase alternating current, a plurality of impulse transformers each arranged to transform a different phase,.and an output circuit associated with the secondaries of said impulse transformers.

10. An apparatus for producing radio frequency current, comprising a source of polyphase alternating current, a phase. multiplying transformer connected to said source, a plurality of impulse transformers connected to said phase multiplying transformer, a Jlurality of oscillating circuits, each including a secondary of one of said impulse transformers, and an output circuit inductively connected to said oscillating circuits.

11. An apparatus for producing radio frequency current comprising a source of polyphase alternating current, means for multiplying the number of phases of said cur rent, means for separately transforming the latory circuit associated with each transformer and containing the transformer secondary and an output circuit connected to all of said plurality of oscillatory circuits.

In testimony whereof I have hereunto set my hand at Washington, D. C, this 18th day of January, 1918.

LEONARD F. FULLER.

In presence of XVASHINGTON DODGE. 

